Entoto is one of a handful of sites put forward as a possible location for a medieval imperial capital known as Barara. This permanent fortified city was established during the early-to-mid 15th century, and it served as the main residence of several successive emperors up to the early 16th-century reign of Lebna Dengel. The city was depicted standing between Mounts Zikwala and Menegasha on a map drawn by the Italian cartographer Fra Mauro in around 1450, and it was razed and plundered by Ahmed Gragn while the imperial army was trapped on the south of the Awash River in 1529, an event witnessed and documented two years later by the Yemeni writer Arab-Faqih. The suggestion that Barara was located on Mount Entoto is supported by the very recent discovery of a large medieval town overlooking Addis Ababa located between rock-hewn Washa Mikael and the more modern church of Entoto Maryam, founded in the late 19th century by Emperor Menelik. Dubbed the Pentagon, the 30-hectare site incorporates a castle with 12 towers, along with 520 meters of stone walls measuring up to 5-meter high.
The site of Addis Ababa was chosen by Empress Taytu Betul and the city was founded in 1886 by Emperor Menelik II. Menelik, as initially a King of the Shewa province, had found Mount Entoto a useful base for military operations in the south of his realm, and in 1879 he visited the reputed ruins of a medieval town and an unfinished rock church that showed proof of the medieval empire's capital in the area before the campaigns of Ahmad ibn Ibrihim. His interest in the area grew when his wife Taytu began work on a church on Mount Entoto, and Menelik endowed a second church in the area.
However, the immediate area did not encourage the founding of a town for lack of firewood and water, so settlement actually began in the valley south of the mountain in 1886. Initially, Taytu built a house for herself near the "Filwoha" hot mineral springs, where she and members of the Showan Royal Court liked to take mineral baths. Other nobility and their staff and households settled in the vicinity, and Menelik expanded his wife's house to become the Imperial Palace which remains the seat of government in Addis Ababa today. The name changed to Addis Ababa and became Ethiopia's capital when Menelik II became Emperor of Ethiopia. The town grew by leaps and bounds. One of Emperor Menelik's contributions that are still visible today is the planting of numerous eucalyptus trees along the city streets.
Following all the major engagements of their invasion, Italian troops from the colony of Eritrea entered Addis Ababa on 5 May 1936. Along with Dire Dawa, the city had been spared the aerial bombardment (including the use of chemical weapons such as mustard gas) practiced elsewhere and its railway to Djibouti remained intact. After the occupation the city served as the Duke of Aosta's capital for unified Italian East Africa until 1941, when it was abandoned in favor of Amba Alagi and other redoubts during the Second World War's East African Campaign. The city was liberated by Major Orde Wingate and negus Haile Selassie for Ethiopian Gideon Force and Ethiopian resistance in time to permit Emperor Haile Selassie's return on 5 May 1941, five years to the day after he had left. Following reconstruction, Haile Selassie helped form the Organisation of African Unity in 1963 and invited the new organization to keep its headquarters in Addis Ababa. The OAU was dissolved in 2002 and replaced by the African Union (AU), which is also headquartered in the city. The United Nations Economic Commission for Africa also has its headquarters in Addis Ababa. Addis Ababa was also the site of the Council of the Oriental Orthodox Churches in 1965.
Ethiopia has often been called the original home of mankind because of various humanoid fossil discoveries like the Australopithecine Lucy. Northeastern Africa, and the Afar region in particular, was the central focus of these claims until recent DNA evidence suggested origins in south central Ethiopian regions like present-day Addis Ababa. After analysing the DNA of almost 1,000 people around the world, geneticists and other scientists claimed people spread from what is now Addis Ababa 100,000 years ago. The research indicated that genetic diversity decreases steadily the farther one's ancestors traveled from Addis Ababa, Ethiopia.